Place a yoga mat on the floor and lie down on your back. Raise your legs up towards the ceiling to form a 90 degree angle with the floor. Crunch your abs and reach up with both hands to touch your toes while holding the same position. Alternatively, raise both legs towards the ceiling. Then bring them both down together until they are four inches off the floor. Pause and breathe, then bring your legs back to the starting position and repeat.
Get down on your knees and forearms. Straighten your knees until your body is in a single line. You should aim to hold this position for at least two minutes at a stretch. Raise one leg towards the ceiling whilst in the same position for a greater challenge!
Sit on the edge of a strong chair and place your hands beside your thighs. Tighten your abdominal muscles and bring your feet a few inches off the floor. Now raise your buttocks above the chair while transferring weight to your arms and exercising your abs. Hold this position for as long as possible.
You may also want to read: All the motivation you need to exercise